Optimizing a couples-based mHealth intervention for weight management

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ABSTRACT Weight is a dyadic health issue in married and cohabitating couples. Partners tend to enter this critical interpersonal relationship with a similar weight status and gain weight together over time. Despite this shared risk, standard behavioral interventions focus on individuals, not couples, largely ignoring the inherently dyadic nature of weight management. Early tests of couples weight loss programs lacked a clear conceptualization guiding spouse/partner involvement and results were mixed. Yet there are promising signals – theoretical and empirical – to guide how couples’ relationships can be harnessed to improve weight loss outcomes. The proposed study aims to build on this work and develop an efficacious couples-based mHealth approach to weight loss using the multiphase optimization strategy (MOST) framework. In the preparation phase, we developed a conceptual model drawing on Transactive Goal Dynamics Theory, our own pilot work, and the published literature that includes four dyadic intervention components: dyadic action planning, joint feedback on goal progress, autonomy support training, and home environment modifications. In the proposed optimization phase, we plan to conduct an innovative and efficient factorial experiment to identify which combination of the four dyadic intervention components – when added to the core components of a standard behavioral weight loss program (BWL; e.g., weekly lessons, self-monitoring, feedback) – results in the greatest weight loss at 6 months (primary outcome). The 6-month intervention will be delivered to married and cohabitating couples (N=368 dyads) via a native smartphone app to enhance the reach of the intervention, minimize burden, and attract couples with more demographic and relationship diversity. Assessments will occur at 0, 3, and 6 months. Weight loss and theoretical mediators as framed by Transactive Goal Dynamics Theory (e.g., goal coordination) will be assessed along with hypothesized moderators (relationship and demographic variables). The set of novel dyadic intervention components that maximizes weight loss will be selected for inclusion in an optimized intervention package to be evaluated in a future randomized controlled trial. The proposed study is the first test of a fully mHealth weight loss intervention for married and cohabitating couples. Using the MOST design, it will advance both intervention and theory development by isolating active dyadic intervention components and their mechanisms of action.